Stress is part of daily life;in a national study 40% of respondents reported experiencing stress that day. We know from many studies that stress can affect health, memory, and well-being. But does it affect how we make decisions? And if so, what are the implications-do we become more or less risk averse? Are we more influenced by the potential downsides and less by potential upsides to an option than we would be otherwise? Making decisions involves a complex yet flexible set of brain mechanisms that compute the potential value of options and adjust that value based on the level of uncertainty about the outcome. In this proposal, we examine the effects of acute stress on the basic elements of decision making: the neural signals that predict and represent value, integrate the positive and negative aspects of options, and assess risk based on predicted volatility and uncertainty of options. We test two main hypotheses. The first is that stress makes rewarding stimuli even more attractive and salient, via dopaminergic effects in the ventral striatum. The second is that stress affects risk processing via the insula, but that it has different effects depending on one's sex and age. Some of our most important decisions must be made under stressful circumstances;thus it is paramount that we understand the basic mechanisms of how stress changes the way we evaluate decision options. PUBLIC HEALTH RELEVANCE: Important decisions, such as those regarding personal finances and health care, often involve substantial stress, especially among older adults. The studies in this proposal will provide important information about how stress affects those decisions and how risk averse people are. Making optimal decisions is challenging even under the best of circumstances;these findings should provide critical information for understanding how to improve decision making under stress.